1. Field of the Invention
The present invention relates to a copier, printer, facsimile apparatus or similar electrophotographic or electrostatic image forming apparatus and more particularly to a developing cartridge for use in such an image forming apparatus.
2. Description of the Background Art
One of conventional developing devices for use in an image forming apparatus includes a developing cartridge formed with an opening that faces a photoconductive belt or image carrier. An inlet seal is positioned in the opening of the cartridge for preventing toner from leaking via the opening. A developing roller is rotatable in contact with the belt while a feed roller is rotatable to feed toner to the developing roller. The developing device uses a nonmagnetic, single-ingredient type developer, i.e., toner.
In the developing device of the type described, the developing roller is rotated such that its surface moves upward in the cartridge while the feed roller is rotated in the opposite direction to the developing roller. The feed roller should therefore be positioned in the upper portion of the cartridge. The feed roller so positioned scrapes toner left on the developing roller upward with the result that the toner accumulates in the upper portion of the cartridge. The toner thus accumulated presses the inlet seal to thereby produce a clearance between it and the developing roller, causing the toner to spurt out via the opening of the cartridge.
To prevent the toner from spurting out, the feed roller may be rotated in the same direction as the developing roller so as to scrape the toner left on the developing roller downward, as proposed in the past. This, however, brings about another problem that excessive toner is transferred from the feed roller to the developing roller, degrading the charging ability of the toner and thereby rendering, e.g., a solid image defective. Moreover, the excessive toner also presses the inlet seal and thereby produces the opening mentioned above.
It is an object of the present invention to provide a developing cartridge capable of preventing excessive toner from being transferred from a feed roller to a developing roller and capable of preventing toner accumulated in the upper portion of the cartridge from leaking.
A developing device of the present invention includes a developer carrier for depositing toner on a latent image formed on an image carrier to thereby produce a toner image. A toner feeding member is rotatable in contact with the developer carrier to thereby feed the toner to the developer carrier. A metering member contacts the developer carrier for metering the toner deposited on the developer carrier while a regulating member regulates the toner deposited on the toner feeding member. During development, the developer carrier is rotated such that its surface moves vertically upward at a position where the surface faces an image carrier, while the toner feeding member is rotated such that its surface moves in the same direction as the surface of the developer carrier at a position where the toner feeding member faces the developer carrier.
An image forming apparatus using the above developing device is also disclosed.